{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/106432"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/106432","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Exploring charge carrier dynamics in quantum dot and double heterojunction nanorod light emitting devices using transient electroluminesence measurements","abstract":"Semiconductor nanocrystals are an impressive class of materials showing significant promise for light emitting applications due to their size tunable optical band gap, compatibility with scalable bottom-up colloidal synthesis techniques, and ability to be processed using simple solution-based deposition techniques. Light emitting devices (LEDs) fabricated utilizing these materials have already demonstrated competitive performance with their organic based counter-parts (i.e. OLEDs). One of the more promising nanocrystalline systems to emerge in recent years is the double heterojunction nanorod (DHNR) whose morphology and type-II band alignment has helped to realize multi-functional displays which can both emit as well as detect light. In addition to this functionality, the rod structure can enhance light outcoupling efficiency as compared to the core-shell (CSQD) morphologies. Despite these advantages, the DHNR light emitting devices exhibit similar efficiency losses as their CSQD counterparts, the source of which are attributed to the location and concentration of the different charge carriers residing in the emitting layer. There are still open debates in the quantum dot light emitting diode (QD-LED) community regarding the details of the charge carrier populations which are expected to influence efficiency droop at higher current densities as well as the location and formation of the radiative recombination zone. Despite the importance that charge carrier properties play in the theories invoked to describe device performance, little work has been done to explore the dynamics of the carrier populations under operation. The work described herein helps provide the ground work for studying and interpreting these processes by analyzing the transient electroluminescence (TREL) of both CSQD and DHNR-LEDs. In OLED literature, studying the TREL profile has yielded insight into the motion of carriers through the emitting layer, helped to identify sources of charge traps, and understand device degradation mechanisms which limit operation lifetime of the device. We first study the TREL of CSQD-LEDs and are able to provide insights into the evolution of electrons and holes throughout the different phases of the TREL signal. Through this initial work we identify that the large hole injection barrier and low carrier mobility with the CSQD film govern the main features of the TREL signal. We then demonstrate how the DHNR morphology is uniquely suited to address these issues and highlight ways in which the DHNR structure influences charge carrier dynamics within DHNR-LEDs. We finally make concluding remarks regarding future work involving both the TREL measurement technique as well as how the DHNR structure can be further utilized to study more fundamental aspects of charge carrier dynamics within QD-LEDs.","abstract_html":"Semiconductor nanocrystals are an impressive class of materials showing significant promise for light emitting applications due to their size tunable optical band gap, compatibility with scalable bottom-up colloidal synthesis techniques, and ability to be processed using simple solution-based deposition techniques. Light emitting devices (LEDs) fabricated utilizing these materials have already demonstrated competitive performance with their organic based counter-parts (i.e. OLEDs). One of the more promising nanocrystalline systems to emerge in recent years is the double heterojunction nanorod (DHNR) whose morphology and type-II band alignment has helped to realize multi-functional displays which can both emit as well as detect light. In addition to this functionality, the rod structure can enhance light outcoupling efficiency as compared to the core-shell (CSQD) morphologies. Despite these advantages, the DHNR light emitting devices exhibit similar efficiency losses as their CSQD counterparts, the source of which are attributed to the location and concentration of the different charge carriers residing in the emitting layer. There are still open debates in the quantum dot light emitting diode (QD-LED) community regarding the details of the charge carrier populations which are expected to influence efficiency droop at higher current densities as well as the location and formation of the radiative recombination zone. Despite the importance that charge carrier properties play in the theories invoked to describe device performance, little work has been done to explore the dynamics of the carrier populations under operation. The work described herein helps provide the ground work for studying and interpreting these processes by analyzing the transient electroluminescence (TREL) of both CSQD and DHNR-LEDs. In OLED literature, studying the TREL profile has yielded insight into the motion of carriers through the emitting layer, helped to identify sources of charge traps, and understand device degradation mechanisms which limit operation lifetime of the device. We first study the TREL of CSQD-LEDs and are able to provide insights into the evolution of electrons and holes throughout the different phases of the TREL signal. Through this initial work we identify that the large hole injection barrier and low carrier mobility with the CSQD film govern the main features of the TREL signal. We then demonstrate how the DHNR morphology is uniquely suited to address these issues and highlight ways in which the DHNR structure influences charge carrier dynamics within DHNR-LEDs. We finally make concluding remarks regarding future work involving both the TREL measurement technique as well as how the DHNR structure can be further utilized to study more fundamental aspects of charge carrier dynamics within QD-LEDs.","abstract_has_math":false,"creators":["Rogers, Steven"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Materials Science & Engr","degree_department":null,"school":null,"contributors":["Shim, Moonsub","Huang, Pinshane","Dillon, Shen","Diao, Ying"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-03-02T22:38:38Z","date_published":"2020-03-02T22:38:38Z","updated_at":"2026-07-22T22:24:47Z","subjects":["QLED, CSQD, DHNR, Transient Electroluminescence"],"languages":["en"],"rights":["Copyright 2019 Steven Rogers"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/106432","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Shim, Moonsub","Huang, Pinshane","Dillon, Shen","Diao, Ying"]},{"key":"dc:creator","label":"Author","values":["Rogers, Steven"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-03-02T22:38:38Z","2022-03-02T10:15:15Z","2019-10-29","2019-12"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science & Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["QLED, CSQD, DHNR, Transient Electroluminescence"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2019 Steven Rogers"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/106432"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Semiconductor nanocrystals are an impressive class of materials showing significant promise for light emitting applications due to their size tunable optical band gap, compatibility with scalable bottom-up colloidal synthesis techniques, and ability to be processed using simple solution-based deposition techniques. Light emitting devices (LEDs) fabricated utilizing these materials have already demonstrated competitive performance with their organic based counter-parts (i.e. OLEDs). One of the more promising nanocrystalline systems to emerge in recent years is the double heterojunction nanorod (DHNR) whose morphology and type-II band alignment has helped to realize multi-functional displays which can both emit as well as detect light. In addition to this functionality, the rod structure can enhance light outcoupling efficiency as compared to the core-shell (CSQD) morphologies. Despite these advantages, the DHNR light emitting devices exhibit similar efficiency losses as their CSQD counterparts, the source of which are attributed to the location and concentration of the different charge carriers residing in the emitting layer. There are still open debates in the quantum dot light emitting diode (QD-LED) community regarding the details of the charge carrier populations which are expected to influence efficiency droop at higher current densities as well as the location and formation of the radiative recombination zone. Despite the importance that charge carrier properties play in the theories invoked to describe device performance, little work has been done to explore the dynamics of the carrier populations under operation. The work described herein helps provide the ground work for studying and interpreting these processes by analyzing the transient electroluminescence (TREL) of both CSQD and DHNR-LEDs. In OLED literature, studying the TREL profile has yielded insight into the motion of carriers through the emitting layer, helped to identify sources of charge traps, and understand device degradation mechanisms which limit operation lifetime of the device. We first study the TREL of CSQD-LEDs and are able to provide insights into the evolution of electrons and holes throughout the different phases of the TREL signal. Through this initial work we identify that the large hole injection barrier and low carrier mobility with the CSQD film govern the main features of the TREL signal. We then demonstrate how the DHNR morphology is uniquely suited to address these issues and highlight ways in which the DHNR structure influences charge carrier dynamics within DHNR-LEDs. We finally make concluding remarks regarding future work involving both the TREL measurement technique as well as how the DHNR structure can be further utilized to study more fundamental aspects of charge carrier dynamics within QD-LEDs.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01","The student, Steven Rogers, accepted the attached license on 2019-10-17 at 10:00.","The student, Steven Rogers, submitted this Dissertation for approval on 2019-10-17 at 10:04.","This Dissertation was approved for publication on 2019-10-29 at 13:56.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14495 on 2020-02-28 at 17:35:39","Made available in DSpace on 2020-03-02T22:38:38Z (GMT). No. of bitstreams: 2 ROGERS-DISSERTATION-2019.pdf: 5099670 bytes, checksum: adff305630af10991c96ce346a7e357a (MD5) LICENSE.txt: 4210 bytes, checksum: 4d94986b42a76d1d399692d7963e7985 (MD5) Previous issue date: 2019-10-29","Embargo set by: Seth Robbins for item 113976 Lift date: 2022-03-02T22:39:04Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction set for Item 113976 on 2020-06-17T14:25:26Z with date 2022-03-02 by lac7@illinois.edu.","Limited Restriction set for Item 113976 on 2020-06-17T14:30:20Z with date 2022-03-02 by lac7@illinois.edu.","Limited Restriction Lifted for Item 113976 on 2022-03-02T10:15:15Z."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Exploring charge carrier dynamics in quantum dot and double heterojunction nanorod light emitting devices using transient electroluminesence measurements"]}]}],"canonical_facts":{"dc:contributor":["Shim, Moonsub","Huang, Pinshane","Dillon, Shen","Diao, Ying"],"dc:creator":["Rogers, Steven"],"dc:date":["2020-03-02T22:38:38Z","2022-03-02T10:15:15Z","2019-10-29","2019-12"],"dc:description":["Semiconductor nanocrystals are an impressive class of materials showing significant promise for light emitting applications due to their size tunable optical band gap, compatibility with scalable bottom-up colloidal synthesis techniques, and ability to be processed using simple solution-based deposition techniques. Light emitting devices (LEDs) fabricated utilizing these materials have already demonstrated competitive performance with their organic based counter-parts (i.e. OLEDs). One of the more promising nanocrystalline systems to emerge in recent years is the double heterojunction nanorod (DHNR) whose morphology and type-II band alignment has helped to realize multi-functional displays which can both emit as well as detect light. In addition to this functionality, the rod structure can enhance light outcoupling efficiency as compared to the core-shell (CSQD) morphologies. Despite these advantages, the DHNR light emitting devices exhibit similar efficiency losses as their CSQD counterparts, the source of which are attributed to the location and concentration of the different charge carriers residing in the emitting layer. There are still open debates in the quantum dot light emitting diode (QD-LED) community regarding the details of the charge carrier populations which are expected to influence efficiency droop at higher current densities as well as the location and formation of the radiative recombination zone. Despite the importance that charge carrier properties play in the theories invoked to describe device performance, little work has been done to explore the dynamics of the carrier populations under operation. The work described herein helps provide the ground work for studying and interpreting these processes by analyzing the transient electroluminescence (TREL) of both CSQD and DHNR-LEDs. In OLED literature, studying the TREL profile has yielded insight into the motion of carriers through the emitting layer, helped to identify sources of charge traps, and understand device degradation mechanisms which limit operation lifetime of the device. We first study the TREL of CSQD-LEDs and are able to provide insights into the evolution of electrons and holes throughout the different phases of the TREL signal. Through this initial work we identify that the large hole injection barrier and low carrier mobility with the CSQD film govern the main features of the TREL signal. We then demonstrate how the DHNR morphology is uniquely suited to address these issues and highlight ways in which the DHNR structure influences charge carrier dynamics within DHNR-LEDs. We finally make concluding remarks regarding future work involving both the TREL measurement technique as well as how the DHNR structure can be further utilized to study more fundamental aspects of charge carrier dynamics within QD-LEDs.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01","The student, Steven Rogers, accepted the attached license on 2019-10-17 at 10:00.","The student, Steven Rogers, submitted this Dissertation for approval on 2019-10-17 at 10:04.","This Dissertation was approved for publication on 2019-10-29 at 13:56.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14495 on 2020-02-28 at 17:35:39","Made available in DSpace on 2020-03-02T22:38:38Z (GMT). No. of bitstreams: 2 ROGERS-DISSERTATION-2019.pdf: 5099670 bytes, checksum: adff305630af10991c96ce346a7e357a (MD5) LICENSE.txt: 4210 bytes, checksum: 4d94986b42a76d1d399692d7963e7985 (MD5) Previous issue date: 2019-10-29","Embargo set by: Seth Robbins for item 113976 Lift date: 2022-03-02T22:39:04Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction set for Item 113976 on 2020-06-17T14:25:26Z with date 2022-03-02 by lac7@illinois.edu.","Limited Restriction set for Item 113976 on 2020-06-17T14:30:20Z with date 2022-03-02 by lac7@illinois.edu.","Limited Restriction Lifted for Item 113976 on 2022-03-02T10:15:15Z."],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/106432"],"dc:language":["en"],"dc:rights":["Copyright 2019 Steven Rogers"],"dc:subject":["QLED, CSQD, DHNR, Transient Electroluminescence"],"dc:title":["Exploring charge carrier dynamics in quantum dot and double heterojunction nanorod light emitting devices using transient electroluminesence measurements"],"dc:type":["text"],"thesis:degree_discipline":["Materials Science & Engr"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:47Z"}